tftp router config over vrf connected network

[notoriousBG]

recently on a DR when I was trying to backup a L3 switch that was located across a GRE tunnel with vrf applied to it, I ran into problems with the tftp source IP not falling within the vrf subnets.

To fix this issue I added the following from a global config prompt: "ip tftp source-interface Vlan2" where vlan 2 is an interface with a vrf instance applied to it.

Config:

version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname lab-3750-tst
!
boot-start-marker
boot-end-marker
!
enable password <removed>
!
no aaa new-model
switch 1 provision ws-c3750-48p
system mtu routing 1500
ip subnet-zero
ip routing
ip dhcp excluded-address 10.100.1.1 10.100.1.19
!
ip dhcp pool VLAN2
   network 10.100.1.0 255.255.255.0
   default-router 10.100.1.1
   dns-server 10.20.31.28
!
ip vrf private
 rd 3:3
!
!
!
crypto pki trustpoint TP-self-signed-3340173440
 enrollment selfsigned
 subject-name cn=IOS-Self-Signed-Certificate-3340173440
 revocation-check none
 rsakeypair TP-self-signed-3340173440
!
!
crypto pki certificate chain TP-self-signed-3340173440
 certificate self-signed 01
  30820247 308201B0 A0030201 02020101 300D0609 2A864886 F70D0101 04050030
  31312F30 2D060355 04031326 494F532D 53656C66 2D536967 6E65642D 43657274
  69666963 6174652D 33333430 31373334 3430301E 170D3933 30333031 30303031
  31305A17 0D323030 31303130 30303030 305A3031 312F302D 06035504 03132649
  4F532D53 656C662D 5369676E 65642D43 65727469 66696361 74652D33 33343031
  37333434 3030819F 300D0609 2A864886 F70D0101 01050003 818D0030 81890281
  8100DD86 579E24C4 F0285158 6CC4CDF8 D8DD3324 20E0BC9E AD5CFAEA A076EDF6
  E4745863 CB144132 3408BFFA 99AB84DD 23E7E2EC 448A9E91 E30E0D6D 136458CE
  AD6323C6 259B61D9 249E9DF1 2B6F2A05 0921A616 8DBBBCC8 A824EF99 593C550E
  0EF970B3 E5C8BE5B FB61E438 2C8360D3 0C292D67 B51FB2BA A284CA4C 699C75A9
  CF4D0203 010001A3 6F306D30 0F060355 1D130101 FF040530 030101FF 301A0603
  551D1104 13301182 0F546F70 656B615F 44525F54 6573742E 301F0603 551D2304
  18301680 14A70CDE 9EEC9B2A 4703E6E9 2DA35DCC 3503629E 2D301D06 03551D0E
  04160414 A70CDE9E EC9B2A47 03E6E92D A35DCC35 03629E2D 300D0609 2A864886
  F70D0101 04050003 81810013 B68BDF20 01B2573F A013BECB 53A5215C EB9DC7E4
  CABE1288 192969CD 855D7147 854C99F0 4F938551 B8B30AF1 7B906753 296611AE
  C446C4EC 2EA2ED4D 1349D4C9 1D0AC3D6 247D0694 E9CFA544 5B4DEB81 FACA1A3A
  F0678B7D 2368299C 0BAF43A3 2D631467 DCF9E7A1 ADE74643 E6A25209 D87EF09B
  9BCB969F 5D925130 B827CA
  quit
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
ip tftp source-interface Vlan2
!
!
interface Tunnel1
 ip vrf forwarding private
 ip address 10.10.128.6 255.255.255.252
 tunnel source FastEthernet1/0/48
 tunnel destination 192.168.218.170
!
interface FastEthernet1/0/1
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/2
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/3
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/4
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/5
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/6
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/7
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/8
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/9
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/10
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/11
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/12
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/13
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/14
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/15
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/16
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/17
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/18
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/19
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/20
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/21
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/22
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/23
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/24
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/25
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/26
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/27
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/28
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/29
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/30
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/31
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/32
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/33
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/34
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/35
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/36
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/37
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/38
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/39
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/40
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/41
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/42
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/43
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/44
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/45
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/46
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/47
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet1/0/48
 no switchport
 ip address 10.20.105.254 255.255.255.0
!
interface GigabitEthernet1/0/1
!
interface GigabitEthernet1/0/2
!
interface GigabitEthernet1/0/3
!
interface GigabitEthernet1/0/4
!
interface Vlan1
 no ip address
!
interface Vlan2
 ip vrf forwarding private
 ip address 10.100.1.1 255.255.255.0
!
ip classless
ip route 0.0.0.0 0.0.0.0 10.20.105.1
ip route vrf private 0.0.0.0 0.0.0.0 10.10.128.5
ip http server
ip http secure-server
!
!
control-plane
!
!
line con 0
line vty 0 4
 password <removed>
 login
line vty 5 15
 login
!
end